Trang An is an eco-tourism destinations in the world heritage population Trang An Ninh Binh province . It was the Government of Vietnam national relic is especially important and recognized as a UNESCO World Heritage Site since 2014. Chang'an dual called the Southern capital of Hoa Lu ancient capital , is now trying Hoa Lu ancient capital . Trang An system limestone mountains geological age about 250 million years , over a long period of weathering by the transformation of the earth , climate , transgression , marine degradation brought in their hundreds of valleys , caves activities , swimming dress . In this landscape there are many wetland ecosystems , forests and limestone monuments linked to the history of the ancient capital of Hoa Lu